Messages

1186

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 29, 2012, 10:54:04 AM »

they are not either at the top or bottom, sensor are linear capture, not like film, the range is larger vs smaller, that is the difference and if you care more about highlights then you expose less and save more, if you care more about shadows you expose longer and lose more highlights

If your talking strictly about discrete levels, yes, but technically speaking you could make the same argument about film. Were talking about dynamic range, though...successive stops of increased tonal range. Every additional bit IS a doubling of the total DR, so in that sense, no, its not linear.

and don't forget that DxO "print" numbers are based on a normalization to 8MP so you can things like 14.5 stops on a 14bit camera

I'd like to know exactly how the simple act of downscaling magically fabricates additional DR you did not start out with. In the case of the D800, at least according to DXO, you magically gain a full 2/3rds of a stop extra DR simply by scaling all of your images down to an 8x12" print. Well, either you can gain what you don't have with a little bit of resizing-foo...and that would apply to ALL cameras,  including Canons; or no amount of digital magic can fabricate DR, and Mount Spokane is absolutely correct that DXO is weighting their results in favor of Nikon. Seeing as the gains Nikon has made with the D800 surpass what seems plausible and reasonable, my commitment to DXO's print DR (which I previously trusted) is wavering.

Personally, I'm of the camp that if you start out with 13.8 stops of native DR strait off the sensor, you have 13.8 stops of DR. If you muck around with a digital image in post to fabricate additional data, that is not true dynamic range, and technically speaking you should be able to do the same thing with images from ANY camera to magically increase DR. In this case, DXO claims about 1.6 times as many additional levels of luminance than you got strait out of the camera...around an additional 10000 levels!! For the math, 1 extra stop of DR is 2^15, or 32768 levels, where as 14 stops of DR is 2^14, or 16384 levels, so a gain of 2/3rds of a stop is 2^15 - 2^14 * 2/3. Sorry, but mathematically, you don't gain that much additional fidelity simply by scaling your image down. DXOMark is "fiddling".

1187

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 29, 2012, 10:42:10 AM »

Every additional bit of DR doubles the number of luminance steps you can achieve...and they are pro-actively allocated to HIGHLIGHTS FIRST, then to darker tones.

Yes, and because of this I assumed a 12-stop DR (i.e. 5D3) to have a brightness range of [4,16383] and 14-stop (i.e. D800) a range of [0,16383], in which case I considered the highlight range to be equal. My understanding is that the extra stops that the D800 offer are primarily in the bottom end of the DR due to lower read noise etc.

True, the 5D III would have twelve stops because it loses something on the shadow end. That wouldn't really mean that the most common usage of DR is for shadows, though. It would simply mean that shadows are the greatest area of gain were Canon to improve their DR at all.

Most of the blather that ensued on this forum shortly after the 5D III announcement was people complaining about the bottom 2-3 stops of DR, which generally account for maybe 20 or so distinct levels?

This was my original point, people (and apparently DXO) are making a big deal of the extra 2 stops (4 levels in total, 3 stops bottom DR would be 8 levels), when in the real world it doesn't matter at all since the brightness data is quantized beyond repair. I'm not usually very good in making my point clearly :-)

Yup, that would be entirely true as well. Its amazing what a few bits worth of least-significant data containing  0.001% of the grand total number of levels can do to people and markets.

1188

EOS Bodies / Re: Canon 5D III RAW @12800 w/ NR in LR4

« on: March 29, 2012, 02:23:49 AM »

Please remove the ending dot from your URL

HAH! Sorry, fixed. (Damnable periods... )

1189

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 29, 2012, 02:11:20 AM »

Oh Ok I'm now interpreting you as criticizing the fact it's a linear 14 bit fixed point encoding scheme coming off the ADCs. Well there's absolutely nothing wrong with linear encoding if it encompasses the full dynamic range of the photocell. Using a floating point encoding scheme would usually be done to throw information away, i.e. compress the data that was less interesting. Since we are interested in every gradation of the visible light spectrum equally, using linear encoding is the high end way to do it, not a compromise.

I'm not saying there is anything wrong with it, I'm just saying that to make a big deal about a 2-stop advantage with this technology is wrong :-) The two stops don't help much with the most common use case for DR, which is to recover shadow detail.

I would STRONGY dispute that the most common use case for DR is to recover shadow detail. Canon purposely caters their DR to the highlights, as its only in the highlights where you can literally CLIP information and prevent any recovery at all (you literally can't "clip" at the black end such that detail is unrecoverable...you can only compress blacks together and possibly mash blacks into the noise floor, but even then, you usually can still recover something, and with dark frames, you have the potential to recover a lot.) Every additional bit of DR doubles the number of luminance steps you can achieve...and they are pro-actively allocated to HIGHLIGHTS FIRST, then to darker tones. Most of the blather that ensued on this forum shortly after the 5D III announcement was people complaining about the bottom 2-3 stops of DR, which generally account for maybe 20 or so distinct levels? Highlights have thousands of levels allocated to them, and the more the better from a raw theoretical standpoint. Dynamic range is NOT primarily allocated to the shadows, particularly in Canon cameras (the 5D line itself is a supreme example of why...as it's extremely popular with wedding photographers, who without question need highlight range more than shadow range for bright white wedding dresses, shiny brides maids and the like.)

The arguments for shadow DR primarily come from landscape photographers and a few more niche markets, who tend to shoot scenes with dynamic ranges that (sometimes far) exceed the range of a camera. Regardless of how much DR you have, unless you are lucky enough to find a sunrise or sunset at exactly the right time where you only need about two extra stops, your going to have to compromise on shadows vs. highlights, and the best way to compensate is with graduated neutral density filters (even if you have 14 total stops of usable DR.) Landscape photographers, however, do not make up the vast majority of actual or potential 5D III users.

1190

EOS Bodies / Canon 5D III RAW @12800 w/ NR in LR4

« on: March 29, 2012, 01:55:24 AM »

Someone in the photo.stackexchange.com chatroom posted this link to a 5D Mark III High ISO test: http://johncarnessali.com/lens-tests/3201.

For being ISO 12800, the non-NR versions look pretty darn good. Much better than I've ever seen out of my 7D @ ISO 3200, and in many cases better than I've seen with my 7D @ ISO 1600.

1191

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 29, 2012, 12:27:58 AM »

How can you possibly attempt to objectively judge a medium (photography) that's so inherently subjective?

HAHA! You nailed it!! 

1192

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 28, 2012, 11:14:17 PM »

@V8Beast: I guess my point got lost in all the rest.  To keep things simple:

* DXOMark-type results generally represent empirical tests that compare hardware in a statistically accurate manner.

* DPReview-type results generally represent real-world tests that compare hardware in a practical manner.

* Personal observation results generally represent opinions that may or may not jive with the opinions of others.

All three of the above forms of evaluation are valuable. Even personal observations are very valuable, as under close scrutiny most photographers can tell the minor differences between cameras. (How they interpret those differences, and whether they choose to see one camera or another as better, is where subjectivity comes into play.) Real-world tests provide value in that they allow us to perform practical comparisons of gear in situations that we can relate to. Empirical tests provide value in that they allow us to evaluate information well beyond what may be practical, real, or even meaningful.

Everyone has their opinions about DXOMark, DPR, and subjective opinion, and not everyone uses ALL of the sources of information available to formulate their own opinions. I'm just saying that while DXOMark's results may seem odd, may jive with each other at times and wildly contradict each other at other times, most of their data is still consistent and empirical in relation to themselves, and that has value. I wouldn't recommend using their numbers as a sole source of information, though...they DO tend to be rather odd at times.

1193

Lenses / Re: What lens are you patiently waiting for?

« on: March 28, 2012, 09:07:54 PM »

Personally, as I've become a hard-core bird photographer (it consumes my every free moment), I'm waiting for something that would actually improve my bird photography. The 100-400mm f/4.5-5.6 is an excellent lens that currently services my needs well, however seeing as the proposed update to it, an f/4-5.6 aperture lens, doesn't improve anything on the long end (where I spend the very vast majority of my time), it doesn't seem that valuable. So, I figure, if I'm going to spend a ton of money on a lens, it might as well be something worthwhile:

Canon EF 600mm f/4 L IS II

I figure by the time they actually release the darn thing, I'll have enough money to buy one outright, along with the 1.4x and 2x TC III's and a gymbal tripod mount.

1194

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 28, 2012, 08:55:00 PM »

If Nikon were a big customer of yours, and Canon was not, what would you do? 
 
I sure wouldn't give Canon better ratings.  The DXO mark has weightings assigned to different sensor chacteristics, and is easy to rig.  If one had something to gain by it, that is.
 
http://www.dxo.com/us/image_quality/customers2

Fair point. I actually think they DO unfairly weight their "print DR" numbers. I think that becomes blatantly obvious with the D800's 14.4 stops of DR, which is 0.4 stops beyond what is theoretically possible with a 14-bit sensor. (Since every bit is a doubling of the numerical space of the one before it, mathematically, it would be impossible to actually achieve 14.4 stops of DR, as it would require a 15th bit of numeric precision (something we know is not the case)...unless you are doing something rather unscrupulous.)

(I have also often wondered why they call it "print DR"...when in reality, an actual print would be far more limited in terms of DR than a camera...to around 5-7 stops in most cases on all but the absolute BEST papers, supporting the highest dMax imaginable, with the most cutting edge of pigment ink technologies.)

1195

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 28, 2012, 08:38:10 PM »

Here are two samples images of black cars, one shot with a 5DC and the other with a 7D. Both images were taken with the same 70-200 f/4L, on bright sunny days, within 45 minutes of sunset. So the variables in light quality and lens quality is next to zero. Both images are out-of-camera raws converted to jpegs with no post processing.

According to DxOMark, the 7D has 11.7 stops of DR, while the 5DC has 11.1 stops. Call me crazy, but the the 5D seems to pull out substantially greater shadow detail, especially in the foliage. IMHO, the difference is so obvious I don't even have to label which image came from the 5D, and which came from the 7D. I very much prefer the color and contrast of the 5D's images, but again according to DxOMark, the overall sensor scores between both bodies is very similar (66 vs. 71).

I think this is right here demonstrates exactly why DXO has something to offer. Your opinion here is simply that...your opinion. If you actually held a poll about those two photographs, I would be willing to bet that you would NOT get a 90%/10% ratio, where most people could tell just by looking at those photographs which was which. I would bet such a poll would end up closer to a 60%/40% ratio. That wouldn't be entirely because how each of us sees is subjective, but also due to the differences in computer screens, computer screen calibrations, etc. To me, those photos look relatively similar, however I have a calibrated screen tuned for post-processing photographs for final print. Because I print and judge my print qualities from how things look on-screen, the blacks in those photos look pretty even-keel. I'd be willing to bet, however, that one of them would indeed stand out as having "better" blacks if I viewed it with the screens I have at work, as they are calibrated for an entirely different purpose, and are a bit lower contrast (which would enhance shadow details.)

There is also the simple point that we don't know for sure how dark the deepest shadows are in the leaves of the trees of the 5DC shot. They may look "better" simply because they are not nearly as deep as the ones the 7D had to work with. That may be the case with all the 5DC shadows, where as the 7D may have had to deal with deeper shadows everywhere. You can't really make an objective comparison with two entirely different shots like that...you don't know for sure exactly how the shadows of each shot compare. You need a consistent, calibrated photographic source to properly measure the differences (even if they are "useless differences"), and that would be an area where DXO excels.

DXO mark publishes low-level measurements run through a standard set of mathematical formulas. While their numbers may seem odd, I find them valuable at times if for no other purpose than to demonstrate that physical hardware specifications make a picture not. The best example are DXO's MF camera ratings, which generally appear rather crummy compared to the latest and greatest from Sony, Nikon, and Canon. Empirically, modern-day digital MF sucks (regardless of niche.) Practically, they are still the best money can buy (by a long shot) for the niches they service.

1196

EOS Bodies / Re: LensRentals.com RESOLUTION TESTS

« on: March 28, 2012, 06:50:49 PM »

I agree with the others here; It is really educational, and I really like when people are willing to get into the essence of things. That said, I realise that a lot of this is far over my head, but that does not diencourage me, rather, I realize that there are new interesting things to learn about.

You said that there is nothing one can do about photon noise, and that struck me as strange. You are probably right, but as a general rule I am sceptic to deterministic statements. If there is one thing we have learned from the history of science, - is that what at a certain point in time seemed to be impossible, are suddendly resolved. I will not quote Kuhn here, but reconfigurations of knowledge, old discarded ideas are brought to life again with the support of supplementary technology and knowledge and so forth..  Just a thought.

Sorry, I should have included proper context in regards to photon noise. In that, I mean with current types of sensor technology, not "period". There are actually some pretty intriguing ideas for new types of sensor design that may indeed help us resolve some of the "photon shot noise" problem. One of the ones I like most is DFS or Digital Film Sensors. The general idea is that instead of having pixels that are always relatively large, use pixels that are times smaller than we have now (sub-micron size), and when a photon strikes just one pixel, activate a "digital grain"....similar to how silver halide in film works. As more photons strike pixels in that particular grain, the grain as a whole would accumulate "charge", and therefor intensity. The genius about this approach is that it is highly flexible, and you can do some amazing things. The original article (http://ericfossum.com/Publications/Papers/Gigapixel%20Digital%20Film%20Sensor%20Proposal.pdf) did not really go into detail about how that approach might be capable of addressing various types of noise, however you could do something along the lines of arbitrary sub-"grain" splits, dividing very large "grains" into smaller "grains" as light became more evenly distributed across the sensor, allowing resolution to grow dynamically as the characteristics of incoming light permitted. You might also be able to do some hardware-level pixel (sub-"grain") level redistribution of charge to normalize photon shot noise across neighboring pixels, so long as they did not affect "grains" above a certain level of granularity (i.e. the adjustment of charge did not affect a configurable level of resolution/did not blur detail above a certain level of fineness.)

1197

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 28, 2012, 04:45:38 PM »

Personally I am not convinced about the DxO measurements - they dont pass the common sense tests

I tend to agree. Their website shows Nikon d700 rated at 80 and 5D Mark II at 79?

DXO's tests are very consistent in terms of the numbers they pump out. They should never really be taken as "real-world" results, as they are not. The only real value to DXO numbers is their consistency, which makes it easy to compare the raw, low-level capabilities of any camera, regardless of make or model. Thats handy...to a degree. Just make sure to salt generously in comparisons like the one above, and in general, DPR is probably a MUCH better measure of real-world performance than DXO.

1198

EOS Bodies / Re: LensRentals.com RESOLUTION TESTS

« on: March 28, 2012, 02:20:11 PM »

jrista, FANTASTIC TEACHING! Thank you! Is this actually your profession or your hobby? I think you should post a small summary into Nikonrumors. Or it should be linked to the D800 manual

Aye, your welcome. This is really just a hobby...I like to know how things work.

I'd love to post a summary to Nikon rumors, however I'd probably get flamed into oblivion. Keep in mind, the D800 is actually a lower spatial resolution than the 7D by a fair percentage (you would need a 47mp FF sensor to have 4.3 micron pixels), and as such, its still well within the realm where it can produce very nice, sharp photos, so it really is a good camera...just keep in mind, it has about 87% the resolution of the 7D, so the 7D is pushing the limits quite a bit more than the D800 is. I wasn't trying to indicate people should not buy a D800, actually I think its an excellent camera for those who explicitly need high quality, high resolution photographs.

This sound perfectly like the Theory of Constraints! http://en.wikipedia.org/wiki/Theory_of_constraints

I think a number of persons need to read this detail jrista has gone into.

YUP! The theory of constraints applies to a lot of things. Its actually rather sad that it is referred to rather infrequently in general theory of things like Cameras.

jrista, Thank you! you just cured my "24 megapixelitis for 7D2"! 

  Glad to be of service. To qualify that, though....if Canon could produce a 24mp APS-C sensor that had considerably less noise than the 7D, and supported an extra stop or two of high ISO...I'd buy one. The 7D is at limits as much because its pushing resolution as it is because its electronic noise is a bit too high for that resolution. Electronic noise and an aggressive low-pass filter does eat into the "fine" detail that the 7D is theoretically capable of resolving. Nothing you can do about photon noise, but improving electronic noise would make a higher resolution 7D II sensor more capable of recording that finer level of detail that a similar-megapixel FF sensor could not resolve. If a 24mp 7D II was capable of cleanly resolving super fine detail (which the current 7D is marginally able to do), then it WOULD still be worth it.

1199

EOS Bodies / Re: Any thoughts on how the 5d3 will compare on dxo mark to the Nikon D800?

« on: March 27, 2012, 09:14:49 PM »

What is the limit of sRgb then?

In what context? (There weren't any quotes there, so I'm not sure where this conversation continues from.)

Generally speaking, sRGB is a color space, which doesn't so much as change the number of representable colors...rather it changes the saturation and luminosity extents and white & black point of colors when modeled within that color space. You'll always have 24bits (8-bit RGB) or 48bits (16-bit RGB) of integer precision for each pixel, however with say AdobeRGB or ProPhotoRGB, the appearance of those colors when rendered may differ in comparison to sRGB, despite, technically, being "the same" color. In larger color spaces, a fully saturated "red" may appear more red and more saturated than in sRGB (and whether you have the ability to actually observe that would depend on whether your viewing device supports a gamut larger than sRGB itself!  )

Image Color Management (ICM) converts color information from one color space to another in L*a*b* (Lab) space, and colors are usually represented as high precision floating point numbers when doing so...so the number of mathematically representable colors is essentially "infinite". When converting back out of Lab to RGB, you may lose precision, and depending on the distribution of specific floating point color values in Lab, discrete color values in RGB may coalesce or end up clipped (sometimes depends on rendering intent, such as Absolute, Relative, or Perceptual.) Hence the reason why its useful to keep photos in the widest gamut (color space) possible until you actually have a reason to convert to sRGB (a smaller gamut.)

1200

Site Information / Re: Bring Back Karma – NOW!

« on: March 27, 2012, 08:58:57 PM »

Karma is really a sketchy thing, and difficult to nail down whether it was valuable or not. I was pretty even with karma for a while, and when I started bringing science, math and a little factual reference to the table, my smites grew to double my applauds. I don't think people like having their shiny, etherial wonder-worlds where everything they believe in their heads is also exactly true in reality (be it about something they hate or love), and when someone bursts that bubble with a little honesty or truth, they smite smite smite! I'd figure thats how a guy like Neuro has 80% as many smites as he has applauds...people don't like having their fanciful bubbles burst, even if they are burst with factually valid information.

I personally ignored karma most of the time. In some cases you might see someone with 5 applauds and 50 smites and their posts were pretty reasonable, just not what people wanted to hear. In other cases you might see someone with 50 applauds and 5 smites, and they were a raging troll. Then there were the even keelers like Neuro, or briansquibb (who seemed to have a null rating at all times, equal applauds as smites), when most of the time he was just trying to keep the mood light, and half the rest of the time he was keeping people honest.

I think a better system might be a LIKE system, with a "reported violations" rating off in some other place (i.e. the Like and Report Violation links far away from each other.) Likes can only be positive, and would generally only be given when someone posts something useful. Reports, if done right, would be harder to issue and hopefully would only be used in cases where someone was blatantly a troll out for lulz, or other offenses. Both rankings would be shown, kind of like applaud and smite, but hopefully "reports" would be far less frequent in most cases.